Method of attaching pliant web to thermoplastic base



United States PatentOffice 3,514,350 Patented May 26, 1970 3,514,350 METHOD OF ATTACHING PLIANT WEB T THERMOPLASTIC BA E ,John W. H. Bishop, Montreal, Quebec, Canada, assignor ABSTRACT OF THE DISCLOSURE A method of attaching a pliant web to athermoplastic base utilizing a sonic element to press the web to the base, at the same time causing the base to melt and the web to adhere to the base.

This invention relates to attaching a pliant web, such as a business machine inking ribbon, to a thermoplastic base, such as the hub of a thermoplastic spool.

The attachment of the bitter end of a business machine inking ribbon to a spool has been a problem which has led to many solutions, none of which has been entirely satisfactory. The problem is, moreover, of increasing importance at this time in view of the rapid expansion of the business machine industry, and there is presently great need for low cost, high speed production of business machine inking ribbons wound on spools having a wide variety of shapes and sizes.

With the advent of the plastic spool a few years ago, efforts were made to heat-seal the bitter end of the inking ribbon to the hub of the spool, as such a technique would lend itself to highly automatic operation and would simplify the mechanical procedures required in attaching the ribbon to the spool. In the efforts to use a heated element pressing the ribbon against the hub of the spool and thus melt the hub and seal the ribbon, it was found that it was not possible to effect such a seal as the ribbon was destroyed at the point of contact of the heated element before effective melting of the hub took place.

In accordance with the present invention, it has now been found that heat-sealing of an inking ribbon to a thermoplastic hub by melting the hub momentarily while pressing the ribbon against the hub can effectively be accomplished using a pressure element which is resonated with a source of sonic vibrations. The shape of the surface, of the pressure element which contacts the ribbon is critical, as a smooth surface does not produce a satis factory seal, but a coarsely roughened surface provides good results.

The joint so formed appears to be formed bythe simple momentary melting of the thermoplastic material at the surface of hub of the spool underlying the points at which the ribbon is pressed against the spool by the rough points of the vibrating element without concomitant destructive heating of the web. Even when thermoplastic ribbons are utilized there does not appear to be extensive melting of the ribbon, and the heating effect appears to be primarily produced in the underlying surface of the hub.

In order to illustrate the range of applicability of the process of this invention, business machines inking ribbons of a number of types and other pliant webs were attached to the hubs of typewriter ribbon spools made of different thermoplastic materials, utilizing a Branson J-17V Plastic Welder. This device operates at a frequency of 20,000 kilocycles having a lead zirconate, titanate transducer for converting electrical signals into mechanical vibrations which are coupled to a catenoidal horn having a /2 inch diameter processing tip at its end. The end of the tip is flattened transversely to its axis and is provided with a knurled face approximately A: inch by inch. The horn itself is half-wave resonant at 20,000 cycles.

Using an inked nylon fabric typewriter, inking ribbon of approximately 1 mil thickness successful attachment was made by pressing the flattened end of the horn against the ribbon onto the hub of the spool while vibrating the horn at 20,000 cycles using spools of the following thermoplastic materials; ethyl cellulose, polystyrene, nylon and polypropylene. Using ribbon spools of the same four thermoplastics, successful seals were similarly made using inked 270 count cotton inking ribbon, 320 count inked cotton inking ribbon and inked silk ribbon. To further illustrate the variety of pliant webs which can satisfactorily be sealed by the method of the presentinvention, a number of seals were similarly madeusing polypropylene spools with white cotton bias tape of approximately 6 mils thickness, dyed cotton bias tape of the same thickness, 1 and 2 thicknesses of heavy, loose-weave black dyed wool ribbon, and polyester backed, carbon ribbon with the carbon side facing the hub of the spool. Other variations successfully tried were photographic backing paper web on an ethyl cellulose hub, photographic film, emulsion side down, on both ethyl cellulose and polypropylene hubs, photographic backing paper web and film together with the film emulsion side down on the hub using an ethyl cellulose hub, and nylon recording tape on an ethyl cellulose hub.

Generally speaking, no criticality as to the required amount of pressure or the time of shot was experienced. It was found, however, if the horn while energized was pressed for a sufficient time to cause smoke to appear, that the ribbon was weakened and a good attachment therefore not achieved. To facilitate attachment it was also found that a flat area on the surface of the hub of the spool at the point of contact was desirable. Generally, the cycle time for best attachment was on the order of 1.2 seconds, the cycle time including the time required to position the spool and ribbon and effect the seal. Best results were obtained using 0.60 second energization of the Branson welder, although this was not critical. In each case, since the point of attachment on the hub was relatively fiat, it was found that the attached ribbons firmly resisted pull from a tangent to the point of attachment on the hub, but could be readily removed from the hub by peeling the ribbon backwards on itself.

While the process of this invention has been described above with reference to a limited number of illustrations, it will be apparent that the process has general applicability in the attachment of pliant web materials to thermoplastic bases.

I claim:

1. The method of attaching a pliant non-metallic web to a thermoplastic spool or hub which comprises pressing said web with an element against said spool or hub, the pressing surface of which element is coarsely roughened, and sonically vibrating said element to cause said surface of said thermoplastic spool or hub to melt and then removing said element.

2. The method of claim 1 on which said thermoplastic spool or hub is polypropylene.

3. The method of claim 1 in which said thermoplastic spool or hub is ethyl cellulose.

4. The method of claim 1 in which said thermoplastic spool or hub is polystyrene.

5. The method of claim 1 in which said thermoplastic spool or hub is nylon.

6. The method according to claim 1 in which said web is an inked business machine inking ribbon.

7. The method of claim 6 in which said web silk ribbon.

8. The method of claim 6 in which said web is an inked cotton ribbon.

9. The method of claim 6 in which said web is an inked nylon ribbon.

10. The method of claim 1 in which said web is a wool fabric.

11. The method of claim 1 in which said web is photographic film.

12. The method of claim 11 in which said web further includes a paper backing web.

is an inked References Cited UNITED STATES PATENTS CARL D. QUARFORTH, Primary Examiner 10 A. J. STEINER, Assistant Examiner US Cl. X.R. 

